Circuit arrangement for the expansion of electrical oscillations



Patented Apr. 11, $6

CIRCUIT ARRANGEMENT FOR THE EXPAN- SION OF ELECTRICAL OSCILLATIONS Henricus Adrianus Broos, Eindhoven, Nether lands, assignor, by mesne assignments, to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application April 12, 1946,- Serial No. 661,520 In the Netherlands May 6, 1943 Section 1, Public Law 690, August 8, 1946 Patent expires May 6, 1963 7 Claims. 1

This invention relates to a circuit arrangement for expanding electrical oscillations. The expression expan is to be construed in the present case to mean the transmission of the electrical oscillations in such a manner that they are stronger transmitted according as their amplitude is larger.

For the expansion of electrical oscillations it is known to make use of a multi-grid tube, for instance a hexode comprising a cathode, a control-grid, a screen-grid, a second control-grid, a second screen-grid and an anode, the oscillations being supplied to the first control-grid and a control-voltage depending on the amplitude of the oscillations being fed to the second control-grid. When the control voltage is applied to the second control-grid with such a polarity that with an increase in amplitude this grid acquires a more positive voltage with respect to the cathode, the oscillations appearing in the anode circuit of the tube are expanded.

The control voltage is obtained by rectifying the oscillations by means of a control rectifier, thus obtaining a direct voltage which depends on the amplitude of the oscillations. When making use of a discharge tube, for instance, a, diode, to constitute the control rectifier, and the rectified voltage is taken from a resistance connected between the anode and the cathode of the diode,

cannot have the same potential, which is oftenobj ectionable.

The invention has for its object to provide a circuit arrangement in which this evil is cured and, consequently, the cathode of the controlrectifier and the cathode of the controlled tube can be kept on the same potential and incorporated in one tube having a common anode.

When making use" of a circuit arrangement comprising a plurality of discharge tubes the cathode of the control-rectifier need not be com mon to that of the hexode, since in this case it may equally well form part of the cathode of another discharge tube.

In a circuit arrangement for the expansion of electrical oscillations by means of discharge tubes comprising a cathode and, reckoned from thecathode onwards, successively at least one firstcontrol-grid, one screen-grid, a second control-grid, a second screen-grid and an anode,

th oscillations being fed to one of the controlgrids and a control-voltage, which depends on the amplitude of the oscillations, being fed to the second control-grid, a resistance is inserted, ac'- cording to the invention, in a circuit common to the two screen-grids, which resistance has sucha size that the mutual conductance of the char-' acteristic curve representing the anode current as a function of the voltage set up at the control grid to which the oscillations are supplied in-' creases with an increase in negative control-' voltage.

Figure 1 of the drawing represents one form of construction of the circuit according to the invention. The oscillations to be expanded are. fed, through the intermediary of the input ter-'- minals I, 2 of the circuit arrangement and a grid condenser 3, to the first control-grid 4 of a dis charge tube 5. The expanded oscillations are set up across a resistance 5, which is inserted in' th anode circuit or the tube, and are taken from the output terminal I, 8. The tube 5 comprises the aforesaid first control-grid 4 and in addition a cathode 9, a first screen grid ID, a second control-grid II, a second screen grid l2, a, suppressor grid l3 which is connected to the cathode 9, and an anode l4. The screen-grid cir-- cuit in common comprises a resistance ll whose: size and consequently the potential of the screengrids is so chosen that the mutual conductance of the characteristic curve, which represents the anode-current as a function of th voltage set up at the control grid, to which the oscillationsare supplied, increases with an increase in nega-, tive control-voltage. A voltage taken from the output terminals 1, 8 is added to the control de-. tector l8. The control-detector consists of a; diode l5 and a resistance 16, by which the anode I, is connected to the cathode of thediode and. through which the control-voltage is taken. The cathode of the diode and the cathode of the dis-f, charg tube 5 have the same potential and the: anode of the diode is connected through a smoothing filter l9 and a constant negative bias 20 to the second control grid ll' of the tube 5.; In the arrangements hitherto known, in which, the resistance I1 is missing, no expansion but compression of the electrical oscillations to be;

transmitted bythe circuit is obtained i. e. oscil- I lations having a large amplitude are amplified by the circuit to a lower degree than oscillations having a small amplitude. In fact, with a decrease in amplitude of the oscillations supplied to the output terminals land 2 the control voltage derived from the oscillations taken from the output terminals i and 8 will decrease so that the voltage vg3' of the second control-grid H increases, and in the circuits hitherto known the mutual conductance of tube 5 increases at the same time, as a result of which the amplification increases. Hence, since the oscillations having a small amplitude are more amplified than oscillations having a large amplitude there occurs compression of the oscillations to be transmitted.

The screen-grid resistance H in common and the resistance 6 of the anode circuit of tube 5 is, accordin to the invention, given such a value that at definite values VgS of the second controlgrid voltage the relation illustrated in Figure 2' exists between the anode current is and the first control-grid voltage Vgl. From Figure. 2v it appears that with a definite value of the first control grid voltage the mutual conductance the. tube decreases as.v the. voltage of the second control-grid vg3 becomes less negative. Consequently, in the circuit. arrangement shown in; Figure 1 the amplification of the. circuit will increase. with an increase in amplitude of the oscillations fed to the. input terminals l and 2,. since in this case the output voltage. and at the. same. time the control voltage increases and the voltage of the second control-grid decreases, so that the. mutual conductance AV and consequently the amplification increases. In this way expansion of the electrical oscillations to be transmitted by the circuit is obtained and notwithstanding that the cathode of the diode I5 and the discharge tube 5 can be kept at the same, potential.

It is not necessary that the oscillations to be expanded are fed to the first control-grid, since they may equally well be fed to the second control-grid.

, From Figure 3 illustrating the relation existing between the anode current and the. secondv control-grid voltage for different values of the first control-grid voltage it appears that in the presence of a constant first control-grid voltage the. mutual conductance becomes higher when the second control-grid voltage falls ofi. In'this' case, in order to secure expansion of the oscillations to be transmitted, the diode I5 of the control detector may be provided again similarly to Figure I. The control voltage initiated across the resistance t5, jointly with the oscillations fed to the terminals I and 2" and to be expanded are supplied to the second control-grid, as shown in Figure 4. In this case the first control-grid must have a constant voltage E with respect to the cathode.

Finally Figure 5 represents another circuit arrangement according to the-invention, in which expansion of the oscillations to be transmitted is obtained again, whilst the cathode of the diode and of the discharge tube- 5 can be kept at the same potential.

This circuit arrangementyieldsa stronger amplification of the oscillations to be expanded. The discharge tube 5 may be. considered as a combination of a triode part comprising the cathode 9, the first control. gridv Q and the first screen-grid l0, and a penthode part including a first screen-grid It, which may be considered as an electron emitting virtual cathode, the. second control-grid H, the second screen-grid 12, the suppressor grid l3 and the anode I l. The control-voltage taken from the resistance 5 is supplied again to the second control-grid l i and the oscillations to be. expanded are supplied to the first control-grid 4. The electrical oscillations amplified by the triode part are taken from the first screen-grid in acting as an anode and are fed, through the intermediary of the second screen-grid 12, to the second control-grid II by means of a potentiometer consisting of a condenser 20, a resistance 2| and a resistance 22. The oscillations are finally amplified by the penthode. part and can be taken again from the output terminals 1 and 8. The expansion of the oscillations to be transmitted is obtained by the control-voltage fed to the second control-grid inthe same manner as set out with reference. to Figure 1.

Since the relation between the control-grid voltages and the anode current. of the discharge tube 5 is not linear the oscillations taken from the output terminals 1 and a will be. distorted. This distortion can be decreased by making. use. of negative back coupling in. a. manner known per se. On account of the negative. back coupling the expansion and. amplification of. the oscillations to be transmitted decreases, it is. true, but this need not be objectionable. in circuits; where the amplification and expansion are considerable such as, for instance, in the. circuit.- shown in Figure 5.

What I claim is:

1. An amplifier circuit arrangement for ex pand-ing the amplitude or an electrical oscillae tion, comprising an electron discharge tube having in the order named a cathode, a first control grid, a first screen grid, a. second control grid. a second screen. grid and an anode, said tube having a characteristic wherein for a. predetermined value of operating. potential on said. first and second screen grids relative to, the potentials: on the. other elements of said tube; the mutual. conductance. of the tube. asv represented. by the anode current-control. grid voltage; ratio increases. with an arithmetic decrease. oi the. control Volt.- age, means. including; a, resistor common to; said. first and said second screen grids. t0 applr operating potentials to said electron, discharge. tube, means, to. apply said oscillation to one. of said control grids, means to derive a. control voltage proportional. to. the amplitude or said, oscillationincluding. a. rectifying. device: having; a cathode connected in common with the cathode of. saidtube and having an anode coupled to theranodeof said tube, and means to apply said voltage to said second control grid, said. resistor having a. resistance value at. which. the potential applied; to said first and second screen grids is substantially equal to said predetermined. value of operating. potential.

2. An amplifier circuit arrangement for expanding the amplitude of an electrical oscillation, comprising an electron discharge tube having in the order named a cathode, a. first control grid, a. first screen grid, a second controlgrid, a second screen grid and an anode, said tube having a. characteristic wherein. for a. predetermined value of operating potential. on said first. and second.

screen grids relative to the. potentials on the.

other elements of said. tube the mutual conductance of the tube as represented by the anode current-control grid voltage ratio increases with an arithmetic decrease of the control voltage,'

means including a resistor common to said first and said second screen grids to apply operating potentials to said electron discharge tube, means to apply said oscillation to said second control grid, means to derive a control voltage proportional to the amplitude of said oscillation including a rectifying device having a cathode connected in common with the cathode of said tube ar se-a6 cathode, a first control grid, a first screen grid, Y

a second control grid, a second screen grid and an anode, said tube having a characteristic wherein for a predetermined value of operating potential on said first and second screen grids relative to the potentials on the remaining ele-- ments of said tube the mutual conductance of the tube as represented by the anode current-control grid ratio increases with an arithmetic decrease of said control voltage, means including a first resistor common to said first and said second screen grids to apply operating potentials to said electron discharge tube, means to apply said oscillation to one of said control grids, a second electron discharge system having a cathode connected to the cathode of said first electron discharge system and an anode coupled to the anode of said first electron discharge system, a second resistor coupled between the anode and cathode of said second electron discharge system to derive a direct control voltage proportional to the amplitude of said oscillation, and means to apply said voltage to said second control grid, said first resistor having a resistance value at which the potential applied to said first and second screen grids is substantially equal to said predetermined value of operatin potential.

4. An amplifier circuit arrangement for expanding the amplitude of an electrical oscillation, comprising a first electron discharge tube having in the order named a cathode, a first control grid, a first screen rid, a second control grid, a second screen grid and an anode, said tube having a characteristic wherein for a predetermined value of operating potential on said first and second screen grids relative to the potentials 0n the remaining elements of said tube the mutual conductance of the tube as represented by the anode current-control grid ratio increases with an arithmetic decrease of said control voltage, a grid-leak resistor coupling said first control grid to said cathode, a load resistor coupled to said anode, a second resistor having one terminal connected to said first and said second screen grids, means to apply operating potentials to said load resistor and the other terminal of said second resistor, means to apply biasing potentials to said first and said second control grids, means comprising a capacitor to apply said oscillation to said first control grid, a second electron discharge tube having a cathode connected to the cathode of said first electron discharge tube and an anode, means coupling the anode of said first electron discharge tube to the anode of said second electron discharge tube, a third resistor connected across the anode and cathode of said second electron discharge tube to derive a direct control voltage proportional to the amplitude of said oscillation, and means to apply said control voltage to said second control grid, said second resistor having a resistance value at which the potential applied to said first and second screen grids is substantially equal to said pre- I determined value of operating potential. v

5. An amplifier circuit arrangement for ex-,

panding the amplitude of an electrical oscillation, comprising a first electrondischarge tube having in the order named a cathode, a first control grid, a first screen grid, asecond control grid,

a second screen grid and an anode said tube having a characteristic wherein for a predetermined value of operating potential on said first and secondscreen grids relative to the potentials on the remaining elements of said tube the mutual conductance of the tube as represented by the anode current-control grid ratio increases with an arithmetic decrease of said control volt-, age, means to maintain said first control grid at a fixed potential with respect to said cathode, a load resistor coupled to said anode, a second re-- sistor having one terminal connected to said first and said second screen grids, means to apply operating potentials to said load resistor and the other. terminal of saidsecond resistor, means to apply biasing potential to said second control grid, means comprising a capacitor to apply said oscillation to said second control grid, a second electron discharge tube having a cathode con-- nected to the cathode of said first electron discharge tube and an anode, means coupling the anode of said first electron discharge tube to the anode of said second electron discharge tube, a third resistor connected across the anode and cathode of said second electron discharge tube to derive a direct control voltage proportional to the amplitude 01 said oscillation, and means comprising a fourth resistor to apply said voltage to said second control grid, said second resistor having a resistance value at which the potential applied to said first and second screen grids is substantially equal to said predetermined value of operating potential.

6. An amplifier circuit arrangement for expanding the amplitude of an electrical oscillation, comprising a first electron discharge tube having in the order named a cathode, a first control grid, a first screen grid, a second control grid, a second screen grid and an anode, said tube having a characteristic wherein for a predetermined value of operating potential on said first and second screen grids relative to the potentials on the remaining elements of said tube the mutual conductance of the tube as represented by the anode current-control grid ratio increases with an arithmetic decrease of said control volt-- age, a grid-leak resistor coupling said first con-- trol grid to said cathode, a load resistor coupled to said anode, a second resistor having one termi-* nal connected to said first and said second screen grids, means to apply operating potentials to said load resistor and the other terminal of said second resistor, means to apply biasing potentials to said first and said second control grids, means comprising a capacitor to apply said oscillation to said first control grid, a second electron discharge tube having a cathode connected to the cathode of said first electron discharge tube and an anode, means coupling the anode of said first aste -we electron: di sch'argetube to'-' the anode I of said second .electrondischarge tube; a third'resistor' connected across the anode and cathode of said second electron discharge tube to derive a direct control: voltage proportional to the amplitude of 2 said oscillation, and means comprising fourth and fifth" resistors connected in series to apply' said control voltage to said second control gridpthe junctionpoint of saidfourtn and firth resistors being couple'cl'to the cathode of said electrondischarge tube, said second'resistor having a resistancevalue at which the potential applied to said first and second'screen grids is substantially equal tosaidpredetermined value of operating potential.

7. An amplifiercircuit'arrangement ror expand'r'n'g' the amplitude of-"an electrical oscillation, comprising afir'st electron discharge tnbe--' havingtin the order named a cathode; a first control grid, 2. first screen grid, a second control grid,- a seco'nd screen grid 'an'd ananode, said tube having a characteristic wherein for a predetermined value of operating potentialon-said i1 first and second screen grids relative to the pothe'mutu'al conductance of the tiibe as -repre sentedlbyi the anode current-control grid ratio i increases with an arithmeticdecreaseof said con trol-Jvoltage, .a grid-leak resistor coupling said first control grid to said cathode, a load resistor coupledto said anode, a second resistor having one terminal connected to said first and said second screen grids; means to apply operating potentials to said'load resistor: and the other terminal of said second resistor,means to apply biasingpotentials to said first and said second control grids, 7 means "comprising a capacitor to applysaid oscillation to said first control grid, a second electron discharge tube havin -acathodeconnected to the cathodeof said first electron discharge=tube=and an anode, means coupling tentialson the remaining elements-of saidtube ing' connected-to said second control grid to applysaid'control voltage to'said second control grid and to apply the amplified oscillation derived irom said second screen grid to said second -control'grid,' said second resistor havinga resistance-value at which the potential applied" to said first and second screen grids is substan tially equal to said predetermined value of operating potential.

HENRICUS ADRIANUS BROOS;

REFERENCES CITED The following references'are of record in the file'of thispatent:

UNITED'sTATE's PATENTS Number Name Date 2,057,857 Steimel et a1 Oct. 20, 1936 2,063,413 Turner Dec. 8, 1936 2,098,405 Sinnett Nov. 9, 1937 2,151,070 Bartels Mar. 21, 1939 2,262,916 Bouoke Nov. 18,1941 2,273,107 Herold Feb. 17, 1942; 2,285,895 Brown 'June 9, 1942 2,285,896 Brown- June 9, 1942 7 2,305,873 Holst Dec. 22, 1942' 

